- bunker silo
- trench silo
There are two types of silos. The horizontal silo is parallel-piped, either cut into the ground (trench silo) or built aboveground (bunker silo). The floor is natural earth or concrete. The walls can be concrete, timber or plywood, or sheet steel. (https://www.britannica.com/topic/farm-building/Buildings-for-machinery-and-supplies#ref558123)